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Graphene is a one-atom-thick sheet of carbon that is a hundred times stronger than steel. (University of Manchester.)

Graphene composites for cars

2014-10-03
Steven Ashley

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Soon after University of Manchester physicists Kostya Novoselov and Andre Geim discovered the "wonder material" graphene—one-atom-thick sheets of carbon that are a 100 times stronger and much lighter than steel—researchers started incorporating it into polymer composites in the hope of creating materials with greatly improved physical properties.

Nearly a decade later, efforts to fabricate practical graphene composites continue apace, but the technology is still in its infancy. Recently, however, a pioneering project began to develop novel graphene-based nanocomposites that one day could truly revolutionize the automotive industry. The 18-month, $1.1-million iGCAuto research collaborative, which is funded by the European Union’s 10-year, billion-euro Graphene Flagship program, aims to make high-performance graphene composites that could reduce the weight of car structures by one-third or more.

Advanced composite materials are widely viewed as a promising way to make vehicles more fuel-efficient and lightweight, but low-mass vehicles tend to perform less well in collisions. So new approaches must be found to enhance the crashworthiness of composites. Graphene composites may be able to fill that role.

The new iGCAuto consortium comprises a half-dozen research groups at the University of Sunderland in Britain, Centro Ricerche FIAT in Italy, Fraunhofer ICT in Germany, Interquimica in Spain and two Italian specialist R&D entities, Nanesa Srl and Delta-Tech SpA.

Lightweighting with graphene

“Graphene has tremendous applications for the automotive industry, and using it to enhance the composite materials in cars has considerable potential,” said Ahmed Elmarakbi, Professor of Automotive Engineering at Sunderland, who wrote the original iGCAuto proposal.

What distinguishes the iGCAuto collaboration are its novel approach and lofty aims.

“We plan to develop a new way to use graphene to enhance polymer composites that we hope can save as much as 30% to 50% in automotive structural weight—the chassis and body-in-white—compared to today’s steel cars,” Elmarakbi said. “In five or six years that improvement could even reach 70%.”

The resulting components could not only lessen weight, but also could feature substantially thinner cross sections as well.

The graphene-based material will be investigated, modeled, and designed to provide improved strength, dimensional stability, thermal behavior, and flame retardance. Fewer smoke emissions is another goal, as is as superior durability—properties that would boost vehicle and occupant safety.

The research team plans to exploit a novel nanocatalyst and unique graphene-based nanocomposite materials that were developed by Egyptian scientist Sherif El-Safty, Chief Researcher at Japan’s National Institute for Materials Science, Elkmarakbi said. “Although we’re at a very early stage and still have to fully prove the concept, I am growing more confident that our collaboration will be fruitful," Elmarakbi said.

El-Safty will not directly take part in this work, but will continue working separately on similar projects.

The multi-national team hopes to develop an enhanced polymer matrix with a modified chemical composition in which the atomic positions and bonding are changed to obtain different physical properties. “Once we achieve that, we will add graphene oxide to form a composite that has better energy-absorption characteristics—microcracking, fragmentation—which should provide improved impact dynamics in collisions and under severe loading,” Elmarakbi said. “Essentially, we’ll functionalize the surface of the graphene oxide to alter the interaction between the oxide and the enhanced polymer.”

New design and production

The iGCAuto members also intend “to change the way composites are manufactured,” Elmarakbi said. “We are currently evaluating different processing concepts, including random dispersion of the reinforcement within the polymer and oriented lay-up processes.”

“Our goal is to combine these novel materials concepts with the latest safety design approaches through the development and optimization of advanced ultra-light graphene-based polymer materials, efficient fabrication and manufacturing processes, and life-cycle analysis to reduce the environmental impact of future vehicles,” Elmarakbi stated. Minimizing costs will be another key objective. In the EU proposal process, the maximum cost allowed for mass reduction was about $24 for each kilogram. Preliminary studies indicate that “we may be able do it without compromising costs.”

Graphene R&D

“This project strengthens our effort to take graphene and related materials from the lab to the factory floor, so that the world-leading position of Europe in graphene science can be translated into technology, creating a new graphene-based industry,” said engineer Andrea Ferrari, Director of Britain’s Cambridge Graphene Center and Chair of the Graphene Flagship’s Executive Board.

“The first experiments with graphene composites occurred in 2006,” he said, “but the research is still in an early phase.” Many fundamental issues still need to be addressed such as processing routes and orientation, but the initial niche applications are appearing. “For example, a line of Head tennis rackets that are made of graphene composites are being used by Novak Djokovic and Maria Sharapova."

Production of graphene itself recently received a boost when a research group at Trinity College, Dublin, led by professor of chemical physics Jonathan Coleman, discovered how to make graphene in a liquid process that is suitable for large-scale production.

“People previously made graphene in small quantities using brute-force methods on graphite, but these methods were inefficient,” he said. “We found that you can produce graphene in a kitchen blender, using fluidic shear to rip the flakes off graphite—a technique that received some public notice a couple of months ago.” Graphite, the ‘lead’ in pencils, is essentially a stack of graphene layers.

“We developed a more practical method in which graphite is first mixed with a solvent (usually water) and soap,” Coleman explained. Then ultrasonic agitation is used to shear off flakes, somewhat like “pressing the side of a deck of cards to slide them off.” The differential shear forces strip graphene flakes, layer by layer, using relatively little energy. “We have licensed that method to a company,” he noted, adding that the liquid exfoliation technique “works with any two-dimensional material.”

Graphene, it turns out, is just the first and best known of a family of so-called two-dimensional (2D) materials—ultra-thin substances that have large lengths and widths, but very small heights. “We know of some five-hundred 2D materials,” Ferrari noted, including silicene, germanene, boron nitride, silicon carbide, rare earths, transition-metal chalcogenides and halides, and synthetic organics.

“The structural applications of graphene hold lots of promise,” he said. Mechanical reinforcement of polymer composites is a “big opportunity for graphene. Even small additions can yield a doubling or tripling of the physical properties.

“I would go so far as to say that if we don’t have significant applications of graphene composites within five years, it would be a big problem for the entire field.”